U.S. patent number 7,515,000 [Application Number 11/895,973] was granted by the patent office on 2009-04-07 for active bias circuit for low-noise amplifiers.
This patent grant is currently assigned to Marvell International, Ltd.. Invention is credited to Xiaodong Jin, Shuran Wei.
United States Patent |
7,515,000 |
Jin , et al. |
April 7, 2009 |
**Please see images for:
( Certificate of Correction ) ** |
Active bias circuit for low-noise amplifiers
Abstract
A low-noise amplifier comprises a first amplification circuit
that includes a control terminal and a first terminal. An impedance
load communicates with the first terminal. A feedback circuit
outputs an output current to the first terminal and that generates
a bias current, which is output to the control terminal and is
based on a difference between the output current and N times a
reference current, where N is greater than zero.
Inventors: |
Jin; Xiaodong (Sunnyvale,
CA), Wei; Shuran (San Jose, CA) |
Assignee: |
Marvell International, Ltd.
(Hamilton, BM)
|
Family
ID: |
37018904 |
Appl.
No.: |
11/895,973 |
Filed: |
August 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
11523423 |
Sep 19, 2006 |
7262665 |
|
|
|
10868064 |
Jun 16, 2004 |
7113043 |
|
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Current U.S.
Class: |
330/279; 330/285;
330/290 |
Current CPC
Class: |
H03F
1/26 (20130101); H03F 1/30 (20130101); H03F
3/343 (20130101); H03F 2200/294 (20130101); H03F
2200/372 (20130101); H03F 2200/504 (20130101) |
Current International
Class: |
H03G
3/10 (20060101) |
Field of
Search: |
;330/279,285,290 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
ANSI/IEEE Std 802.11, 1999 Edition; Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) Specifications; LAN/MAN Standards Committee of
the IEEE Computer Society; 528 pages. cited by other .
IEEE Std 802.11a-1999 (Supplement to IEEE Std 801.11-1999) [Adopted
by ISO/IEC and redesignated as ISO/IEC 8802-11: 1999/Amd
1:2000(E)]; Supplement to IEEE Standard for Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications High-speed Physical Layer in
the 5 GHz Band; LAN/MAN Standards Committee of the IEEE Computer
Society; 91 pages. cited by other .
IEEE Std 802.11b-1999 (Supplement to IEEE Std 802.11-1999 Edition);
Supplement to IEEE Standard for Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications: Higher-Speed Physical Layer
Extension in the 2.4 GHz Band; LAN/MAN Standards Committee of the
IEEE Computer Society; Sep. 16, 1999 IEEE-SA Standards Board; 96
pages. cited by other .
IEEE Std 802.11b-1999/Cor 1-2001 (Corrigendum to IEEE Std
802.11-1999); IEEE Standard for Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications Amendment 2: Higher-Speed
Physical Layer (PHY) extension in the 2.4 GHz Band--Corrigendum 1;
LAN/MAN Standards Committee of the IEEE Computer Society; Nov. 7,
2001; 24 pages. cited by other .
IEEE Std 802.11g/D2.8, May 2002 (Supplement to ANSI/IEEE Std
802.11, 1999 Edition) Draft Supplement to Standard [for]
Information Technology--Telecommunications and information exchange
between systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications: Further Higher-Speed Physical
Layer Extension in the 2.4 GHz Band; LAN/MAN Standards Committee of
the IEEE Computer Society; 47 pages. cited by other .
IEEE P802.11g/D8.2, Apr. 2003 (Supplement to ANSI/IEEE Std
802.11-1999(Reaff 2003)); Draft Supplement to Standard [for]
Information Technology--Telecommunications and information exchange
between systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications: Further Higher Data Rate
Extension in the 2.4 GHz Band; LAN/MAN Standards Committee of the
IEEE Computer Society; 69 pages. cited by other .
IEEE Std 802.11h--2003 (Amendment to IEEE Std 802.11, 1999 Edition
(Reaff 2003)); as amended by IEEE Stds 802.11a-1999, 802.11b-1999,
802.11b-1999/Cor 1-2001, 802.11d-2001, and 802.11g-2003; IEEE
Standard for Information technology--Telecommunications and
information exchange between systems--Local and metropolitan area
networks--Specific requirements--Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) specifications
Amendment 5: Spectrum and Transmit Power Management Extensions in
the 5 GHz band in Europe; IEEE Computer Society LAN/MAN Standards
Committee; Oct. 14, 2003; 75 pages. cited by other .
802.11n; IEEE P802.11-04/0889r6; Wireless LANs, TGn Sync Proposal
Technical Specification; 131 pages. cited by other .
IEEE P802.11i/D10.0, Apr. 2004 (Amendment to ANSI/IEEE Std
802.11-1999 (2003 Reaff) edition as amended b IEEE Std 802.11g-2003
and IEEE Std 802.11h-2003); IEEE Standard for Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements; Part 11: Wireless Medium Access Control (MAC) and
Physical Layer (PHY) specifications: Amendment 6: Medium Access
Control (MAC) Security Enhancements; LAN/MAN Committee of the IEEE
Computer Society; 184 pages. cited by other.
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Primary Examiner: Nguyen; Patricia
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a Continuation of U.S. patent application Ser.
No. 11/523,423, filed Sep. 19, 2006, which is a Continuation of
U.S. patent application Ser. No. 10/868,064, filed on Jun. 16,
2004. The disclosures of the above applications are incorporated
herein by reference in their entirety.
Claims
What is claimed is:
1. A low-noise amplifier, comprising: a first amplification circuit
that includes a control terminal and a first terminal; an impedance
load that communicates with the first terminal; a feedback circuit
that outputs an output current to the first terminal, and that
generates a bias current, wherein the bias current is output to the
control terminal and is based on a difference between the output
current and N times a reference current, where N is greater than
zero; and a first impedance and a second impedance, wherein the
second impedance has an impedance that is N times an impedance of
the first impedance, and the second impedance communicates with the
reference current.
2. The low-noise amplifier of claim 1 wherein the feedback circuit
includes: a comparator that compares a first voltage across the
first impedance to a second voltage across the second impedance,
and that generates the bias current based on the comparison.
3. A low-noise amplifier, comprising: a first amplification circuit
that includes a control terminal and a first terminal; an impedance
load that communicates with the first terminal; a feedback circuit
that outputs an output current to the first terminal and that
generates a bias current, wherein the bias current is output to the
control terminal and is based on a difference between the output
current and N times a reference current, where N is greater than
zero, wherein the feedback circuit includes: a first impedance that
communicates with a voltage reference and the impedance load; a
second impedance having an impedance that is N times an impedance
of the first impedance, wherein the second impedance communicates
with the voltage reference and a reference current source; and a
comparator that compares a first voltage across the first impedance
to a second voltage across the second impedance, and that generates
the bias current based on the comparison; and a capacitance that
communicates with the first impedance, the comparator, and the
impedance load.
4. The low-noise amplifier of claim 1 further comprising: an input
circuit that communicates with the control terminal; and an output
circuit that communicates with the first terminal and the impedance
load.
5. The low-noise amplifier of claim 1 wherein the first
amplification circuit comprises a bi-polar transistor.
6. The low-noise amplifier of claim 4 wherein the input circuit
receives the bias current, and includes a series resistance and a
parallel capacitance that communicate with the control
terminal.
7. The low-noise amplifier of claim 1 wherein the impedance load
comprises an inductance.
8. The low-noise amplifier of claim 4 further comprising: a second
amplification circuit that communicates with the output circuit and
the first terminal of the first amplification circuit, wherein the
first and second amplification circuits are arranged in a cascode
configuration.
9. The low-noise amplifier of claim 8 wherein the second
amplification circuit comprises a bi-polar transistor.
10. The low-noise amplifier of claim 8 wherein a control terminal
of the second amplification circuit communicates with a voltage
reference.
11. The low-noise amplifier of claim 2 wherein the first and second
impedances comprise resistances.
12. The low-noise amplifier of claim 1 wherein the low-noise
amplifier is formed on a monolithic substrate.
13. The low-noise amplifier of claim 1 wherein the low-noise
amplifier is compliant with a standard selected from the group
consisting of I.E.E.E. 802.11, 802.11a, 802.11b, 802.11g, 802.11h,
802.11i and 802.11n.
Description
BACKGROUND
1. Field of the Invention
The present invention relates to integrated circuits. More
particularly, the present invention relates to an active bias
circuit for low-noise amplifiers.
2. Background Information
Typically, in low-noise amplifiers (LNAs) and the like, it is
desirable to reduce the contribution of noise from any component as
much as possible. In bipolar circuitry, for example, a bias current
is applied to the base of the transistor that comprises the LNA.
However, due to process variations, temperature, and the like, the
.beta. of the transistor can vary by a factor of two, three, four
or more. As a result of such varying transistor characteristics,
the level of the bias current required to be applied to the
transistor will change, resulting in a varying control of the gain
of the LNA. Thus, under different conditions and varying transistor
characteristics, the gain of the LNA can vary, which in most
applications is unacceptable.
To address this problem, passive circuitry can be used to control
the bias current applied to the transistor. For example, a diode
device can be connected to the base electrode of the transistor.
Such a diode device has an impedance proportional to 1/G.sub.m. For
a 50.OMEGA. incoming signal, such an impedance can be too low,
which can result in significant signal attenuation. In addition,
any noise generated by the diode device and current sources
connected to it will be transferred to and affect the rest of the
LNA circuit.
Consequently, a biasing scheme is needed that is independent of
process variations, temperature, variations in the .beta. of the
transistor, and other like transistor characteristics.
SUMMARY OF THE INVENTION
A system and method are disclosed for actively controlling the bias
of a low-noise amplifier (LNA). In accordance with exemplary
embodiments, according to a first aspect of the present invention,
a LNA includes a first amplification circuit. The first
amplification circuit includes a control terminal, a first
terminal, and a second terminal. The second terminal is in
communication with a first reference voltage. The LNA includes an
input circuit in communication with the control terminal and an
output circuit in communication with the first terminal. The LNA
includes an impedance load in communication with the output circuit
and the first terminal. The LNA also includes a feedback circuit in
communication with the control terminal and the impedance load. The
feedback circuit includes a current source in communication with a
second reference voltage. The feedback circuit includes a
comparator circuit. The comparator circuit includes a first input,
a second input and an output. The output is in communication with
the control terminal. The feedback circuit includes a first
impedance in communication with the current source and the first
input. The first impedance is configured to generate a
predetermined reference voltage corresponding to a predetermined
reference current generated by the current source. The feedback
circuit also includes a second impedance in communication with the
second input and the impedance load. According to exemplary
embodiments of the first aspect, he feedback circuit compares a
voltage, corresponding to an output current associated with the
first terminal, with the predetermined reference voltage to
generate a bias signal applied to the control terminal for biasing
the low-noise amplifier.
According to the first aspect, the first amplification circuit can
comprise a bi-polar transistor. The control terminal of the first
amplification circuit can comprise a base electrode, the first
terminal of the first amplification circuit can comprise a
collector electrode, and the second terminal of the first
amplification circuit can comprise an emitter electrode. The input
circuit can include, for example, a capacitive element. The
capacitive element can receive an input signal. The LNA can include
an isolation impedance in communication between the control
terminal and the output of the comparator circuit. The isolation
impedance can comprise, for example, a resistive element. The
impedance load can comprise, for example, an inductive element. The
LNA can include a second amplification circuit in communication
between the output circuit and the first terminal of the first
amplification circuit. The second amplification circuit can include
a control terminal, a first terminal, and a second terminal. The
first and second amplification circuits can be arranged in a
cascode configuration. The second amplification circuit can
comprise a bi-polar transistor. The control terminal of the second
amplification circuit can comprise a base electrode, the first
terminal of the second amplification circuit can comprise a
collector electrode, and the second terminal of the second
amplification circuit can comprise an emitter electrode.
According to the first aspect, the LNA can include a third
reference voltage in communication with the control terminal of the
second amplification circuit and each of the first and second
impedances. The first and second impedances can comprise, for
example, resistive elements. A value of the resistive element of
the first impedance can be N times larger than a value of the
resistive element of the second impedance. The feedback circuit can
further include a third reference voltage in communication with the
second impedance, the second input, and the impedance load. The
third reference voltage can include a capacitive element, and a
fourth reference voltage. According to an exemplary embodiment of
the first aspect, the LNA can be formed on a monolithic substrate.
The LNA can be compliant with a standard selected from the group
consisting of I.E.E.E. 802.11, 802.11a, 802.11b, 802.11g, 802.11h,
802.11i and 802.11n, or any other suitable wireless or wired
standard.
According to a second aspect of the present invention, a LNA formed
on a monolithic substrate a first amplification circuit. The first
amplification circuit includes a base electrode, a collector
electrode, and an emitter electrode. The emitter electrode is in
communication with a first reference voltage. The LNA includes an
input circuit in communication with the base electrode. The LNA
includes a first impedance element in communication with the input
circuit and the base electrode. The LNA includes a second
amplification circuit in communication with the collector electrode
of the first amplification circuit. The second amplification
circuit includes a base electrode, a collector electrode, and an
emitter electrode. The first and second amplification circuits are
arranged in a cascode configuration. The LNA includes an output
circuit in communication with the collector electrode of the second
amplification circuit, and a second impedance element in
communication with the output circuit and the collector electrode
of the second amplification circuit. The LNA also includes a
feedback circuit in communication with the first and second
impedance elements.
According to the second aspect, the feedback circuit includes a
current source in communication with a second reference voltage and
a comparator circuit. The comparator circuit includes a first
input, a second input and an output. The output is in communication
with the first impedance element. The feedback circuit includes a
third impedance element in communication with the current source
and the first input. The third impedance element is configured to
generate a predetermined reference voltage corresponding to a
predetermined reference current generated by the current source.
The feedback circuit includes a fourth impedance element in
communication with the second input and the second impedance
element. The feedback circuit includes a third reference voltage in
communication with the second and fourth impedance elements and the
second input. The third reference voltage comprises a fifth
impedance element and a fourth reference voltage. According to
exemplary embodiments of the second aspect, the feedback circuit
compares a voltage, corresponding to an output current associated
with the collector electrode of the first amplification device,
with the predetermined reference voltage to generate a bias signal
applied to the base electrode of the first amplification device for
biasing the low-noise amplifier.
According to the second aspect, the input circuit can include a
capacitive element. The capacitive element can receive an input
signal. The first, third and fourth impedance elements can comprise
resistive elements. The second impedance element can comprise an
inductive element. The fifth impedance element can comprise a
capacitive element. The first and second amplification circuits can
comprise bi-polar transistors. The LNA can include a fifth
reference voltage in communication with the control terminal of the
second amplification circuit and each of the third and fourth
impedance elements. According to an exemplary embodiment of the
second aspect, the LNA can be compliant with a standard selected
from the group consisting of I.E.E.E. 802.11, 802.11a, 802.11b,
802.11g, 802.11h, 802.11i and 802.11n, or any other suitable
wireless or wired standard.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will become
apparent to those skilled in the art upon reading the following
detailed description of preferred embodiments, in conjunction with
the accompanying drawings, wherein like reference numerals have
been used to designate like elements, and wherein:
FIG. 1 is a circuit diagram illustrating a system for actively
controlling a bias of a low-noise amplifier (LNA), in accordance
with an exemplary embodiment of the present invention.
FIG. 2 is a circuit diagram illustrating a system for actively
controlling a bias of a LNA, in accordance with an alternative
exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Exemplary embodiments of the present invention are directed to a
system and method for actively controlling the bias of a low-noise
amplifier (LNA). According exemplary embodiments, a feedback
circuit in communication with the LNA is used. The feedback circuit
senses the current in the LNA. The feedback circuit includes a
comparator for comparing the sensed current with a reference
current. The output of the comparator biases the input of the LNA
by adjusting the current in the LNA until the LNA current reaches a
predetermined level corresponding to the reference current.
Exemplary embodiments of the present invention provide a means of
biasing a LNA that is independent of process variations, transistor
.beta. variations, and other like variations in transistor
characteristics.
These and other aspects of the present invention will now be
described in greater detail. FIG. 1 is a circuit diagram
illustrating a system 100 for actively controlling a bias of a LNA,
in accordance with an exemplary embodiment of the present
invention. The system 100 includes a first amplification circuit
105. The first amplification circuit 105 includes a control
terminal 107, a first terminal 108 and a second terminal 109.
According to an exemplary embodiment, the first amplification
circuit 105 can comprise a bi-polar transistor, such that control
terminal 107 comprises a base electrode, first terminal 108
comprises a collector electrode, and second terminal 109 comprises
an emitter electrode. For example, first amplification circuit 105
can be arranged in a single-ended common emitter configuration such
that second terminal 109 is in communication with a reference
voltage 106 (e.g., a ground or any suitable reference voltage).
The system 100 includes an input circuit 110 in communication with
the control terminal 107 of the first amplification circuit 105.
The input circuit 110 can comprise, for example, a capacitor 112,
or any suitable impedance element or combination of impedance
elements. The system 100 includes an output circuit 115 in
communication with the first terminal 108 of the first
amplification circuit 105. The system 100 also includes an
impedance load 117 in communication with the output circuit 115 and
the first terminal 108. The impedance load 117 can be any suitable
impedance element or combination of impedance elements having any
appropriate values.
The system 100 also includes a feedback circuit 120 in
communication with the control terminal 107 and the impedance load
117. According to exemplary embodiments, the feedback circuit 120
compares a voltage, corresponding to an output current (I.sub.OUT)
associated with the first terminal 108, with a predetermined
reference voltage to generate a bias signal. The bias signal is
applied to the control terminal 107 for biasing the LNA.
According to exemplary embodiments, the feedback circuit 120
includes a current source 125, connected to a reference voltage 127
(e.g., a ground or any suitable reference voltage). The current
source 125 generates a well-controlled and predetermined reference
current I.sub.o of any appropriate value. The feedback circuit 120
includes a comparator circuit 130. The comparator circuit 130
includes a first input 132, a second input 133, and an output 134.
The first input 132 can be, for example, the negative input of the
comparator 130, while the second input 133 can be, for example, the
positive input. The output 134 of the comparator 130 is in
communication with the control terminal 107 of first amplification
circuit 105. The feedback circuit 120 includes an impedance 140 in
communication with the current source 125 and the first input 132.
The impedance 140 is also in communication with a reference voltage
145, such as, for example, a DC power supply voltage (V.sub.DD) or
any suitable reference voltage. The impedance 140 is configured to
generate the predetermined reference voltage corresponding to the
predetermined reference current (I.sub.o) generated by the current
source 125. The feedback circuit 120 includes an impedance 150 in
communication with the second input 133 of comparator 130 and the
impedance load 117.
According to exemplary embodiments, the output current (I.sub.out)
associated with first terminal 108 of first amplification circuit
105 produces a voltage across impedance 150. Comparator 130
compares the voltage across impedance 140 with the voltage across
impedance 150. The output 134 of comparator 130 will adjust the
bias current (I.sub.bias) applied to control terminal 107 of first
amplification circuit 105 until the voltages across impedances 140
and 150 are equal. The impedances 140 and 150 can each be, for
example, resistors, such as resistors 142 and 152, respectively.
However, impedances 140 and 150 can be any suitable impedance
element or combination of impedance elements of any appropriate
values. According to an exemplary embodiment, the value of resistor
142 can be N times larger than the value of resistor 152, where N
can be any number, although resistors 142 and 152 can be any
appropriate value. Thus, the bias current I.sub.bias output by
comparator 130 will adapt to equal NI.sub.o.
The feedback circuit 120 includes a reference voltage 160 (e.g., an
AC ground or any suitable reference voltage). The reference voltage
160 is in communication with impedance 150, the second input 133 of
comparator 130 and the impedance load 117. The reference voltage
160 can include a capacitor 162, or any suitable impedance element
or combination of impedance elements, and a reference voltage 163
(e.g., a ground or any suitable reference voltage). For example,
the reference voltage 160 can be used to filter the reference
voltage 145. The combination of reference voltage 160 and impedance
150 (when comprised of, for example, resistor 152) acts as a RC
filter to reduce noise injection from the reference voltage
145.
The system 100 can include an impedance 155 in communication with
the input circuit 110, the control terminal 107 of first
amplification circuit 105, and the output 134 of comparator 130.
The impedance 155 can comprise a resistor, such as resistor 157, or
any suitable impedance element. The resistor of impedance 155
provides isolation. For example, according to an exemplary
embodiment, the resistor 157 can be 100.OMEGA. and capacitor 112
can be 0.5 pF to match the input of the low gain mode to 50.OMEGA..
However resistor 157 and capacitor 112 can be of any appropriate
values.
FIG. 2 is a circuit diagram illustrating a system 200 for actively
controlling a bias of a LNA, in accordance with an alternative
exemplary embodiment of the present invention. According to the
alternative exemplary embodiment, the impedance load 117 can be,
for example, an inductor, such as inductor 217. However, impedance
load 117 can be any suitable impedance element or combination of
impedance elements having any appropriate values. According to the
alternative exemplary embodiment, the feedback circuit 120 will
adjust the bias current I.sub.bias until the current (I.sub.L)
through inductor 217 reaches the desired level (i.e., NI.sub.o).
The system 200 can include a second amplification circuit 210 in
communication between the output circuit 115 and the first terminal
108 of first amplification circuit 105. The second amplification
circuit 210 includes a control terminal 212, a first terminal 213
and a second terminal 214. According to an exemplary embodiment,
the second amplification circuit 210 can comprise a bi-polar
resistor, such that control terminal 212 comprises a base
electrode, first terminal 213 comprises a collector electrode, and
second terminal 214 comprises an emitter electrode. For example,
the second amplification circuit 210 can be arranged in a common
base configuration, with the control terminal 212 of second
amplification circuit 210 in communication with reference voltage
145. The first and second amplification circuits 105 and 210 are
arranged in a cascode configuration. A cascode configuration
improves stability and linearity and decreases distortion in the
LNA by using the second amplification circuit 210 to shield the
first amplification circuit 105 from voltage changes in the system
200 by improving reverse isolation.
According to an exemplary embodiment, first and second
amplification circuits 105 and 210 can be a n-p-n or p-n-p bi-polar
junction transistors. However, first and second amplification
circuits 105 and 210 can be any suitable type of transistor, such
as, for example, a field-effect transistor (FET), metal-oxide
semiconductor FET (MOSFET), or the like. The reference voltage 145
for the systems 100 and 200 can be set at, for example,
approximately 3V, or any other appropriate value. A regulated power
supply can be used for the LNA to improve supply rejection. The
input signal received on input circuit 110 can be any suitable type
of electrical signal that is capable of communicating electrical
information. The comparator 130 can be implemented using any
suitable means for performing the functions associated with the
component. For example, the comparator 130 can be an operational
amplifier or the like.
The components of systems 100 and 200, or any combination thereof,
can be formed on, for example, a monolithic substrate.
Alternatively, each element, or any combination thereof, can be any
suitable type of electrical or electronic component or device that
is capable of performing the functions associated with the
respective element. According to such an alternative exemplary
embodiment, each component or device can be in communication with
another component or device using any appropriate type of
electrical connection that is capable of carrying electrical
information. In addition, the systems 100 and 200 can be compliant
with standards such as, for example, I.E.E.E. 802.11, 802.11a,
802.11b, 802.11g, 802.11h, 802.11i and 802.11n, or any other
suitable wired or wireless standard.
Exemplary embodiments of the present invention can be used as at
least part of a LNA or any other suitable type of amplifier or
other circuit that requires biasing. For example, exemplary
embodiments can be used in systems for communicating information
over communication channels either wirelessly or by wired means.
However, systems 100 and 200 can be used in any device or system
that communicates information, including both wired and wireless
communication systems, read channel devices, disk drive systems
(e.g., those employing read channel devices), other magnetic
storage or recording applications, and the like, particularly where
an amplifier circuit or the like requires a biasing signal that is
independent of process variations, transistor .beta. variations,
and other like variations in transistor characteristics.
It will be appreciated by those of ordinary skill in the art that
the present invention can be embodied in various specific forms
without departing from the spirit or essential characteristics
thereof. The presently disclosed embodiments are considered in all
respects to be illustrative and not restrictive. The scope of the
invention is indicated by the appended claims, rather than the
foregoing description, and all changes that come within the meaning
and range of equivalence thereof are intended to be embraced.
All United States patents and applications, foreign patents, and
publications discussed above are hereby incorporated herein by
reference in their entireties.
* * * * *